Systems and methods are disclosed for temporal sampling of air exhaled by a user. Some embodiments comprise a
mask adapted to be worn by a user, a chamber, disposed in or on the
mask, the chamber comprising a valve, at least one sensor, disposed in the chamber, for measuring composition of air, an
actuator adapted to open the valve, and at least one processor. The at least one processor is programmed to selectively instruct the
actuator to open the valve, thereby causing air in the
mask to be exposed to the at least one sensor, at a time associated with
exhalation by the user, and to selectively instruct the
actuator to close the valve, thereby preventing air from entering the chamber, at a time associated with
inhalation by the user.